Improved removal of greasy soils is a constant aim for laundry detergent manufacturers. In spite of the use of many effective surfactants and combinations of surfactants, especially when used at low water temperatures, many surfactant-based products still do not achieve complete removal of greasy/oily soils. Lipase enzymes have been used in detergents since the late 1980s for removal of fatty soils by breakdown of fatty soils into tri-glycerides.
Until relatively recently, the main commercially available lipase enzymes, such as Lipolase (trade name, Novozymes) worked particularly effectively at the lower moisture levels of the drying phase of the wash process. These enzymes tended to produce significant cleaning only in the second wash step because the active site of the enzyme was occupied by water during the washing process, so that fat breakdown was significant only on soils remaining on laundered clothes during the drying stage, the broken down fats then being removed in the next washing step. However, more recently, higher efficiency lipases have been developed that also work effectively during the wash phase of the cleaning process, so that as well as cleaning in the second washing step, a significant improvement in cleaning effect due to lipase enzyme can be found in the first wash-cycle. Examples of such enzymes are as described in WO0/60063 and Research Disclosure IP6553D. Such enzymes are referred to below as first wash lipases. Examples of such enzymes include certain variants of lipolase (wild-type Humicola lanuginosa) which should comprise one or more substitutions with positive amino acids near the N-terminal in the three-dimensional structure. The variants should further comprise a peptide addition at the C-terminal and/or should meet certain limitations on electrically charged amino acids at positions 90-101 and 210.
The problem facing the present inventors was how to maximise performance from this new generation of enzymes. The present inventors found that whilst a small benefit could be achieved formulating such enzymes according to present day detergent formulations by simply replacing existing lipase enzymes with the new generation of enzymes, a considerable improvement in performance was found by formulating the detergent compositions in a different way and even reducing the levels of some conventional detergent ingredients.